US6342757B1 - Cathode ray tube for multimedia - Google Patents

Cathode ray tube for multimedia Download PDF

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Publication number
US6342757B1
US6342757B1 US09/691,416 US69141600A US6342757B1 US 6342757 B1 US6342757 B1 US 6342757B1 US 69141600 A US69141600 A US 69141600A US 6342757 B1 US6342757 B1 US 6342757B1
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United States
Prior art keywords
shadow mask
crt
stripes
pitch
stripe
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Expired - Fee Related
Application number
US09/691,416
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English (en)
Inventor
Hyun-jung Shin
Bum-choon Seo
Jong-bin Lee
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Samsung SDI Co Ltd
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Samsung Display Devices Co Ltd
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Publication date
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Priority to US09/691,416 priority Critical patent/US6342757B1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/06—Screens for shielding; Masks interposed in the electron stream
    • H01J29/07—Shadow masks for colour television tubes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2229/00—Details of cathode ray tubes or electron beam tubes
    • H01J2229/07—Shadow masks
    • H01J2229/0727—Aperture plate
    • H01J2229/075—Beam passing apertures, e.g. geometrical arrangements

Definitions

  • the present invention relates to a cathode ray tube (CRT) for multimedia and a method of making the same and, more particularly, to a method of making a multimedia CRT which simultaneously produces high resolution and high brightness for use in both computers requiring high-resolution and televisions or videos requiring high-brightness.
  • CTR cathode ray tube
  • the electron beam emitted from the electron gun passes through the beam-guide apertures of the shadow mask having a color selection function while it is deflected by the deflection yoke. Then it excites the phosphors coated on the panel screen to produce the picture image.
  • a plurality of dot, slit or stripe-shaped apertures for guiding the electron beam are formed on the shadow mask, the shadow mask having a curvature ratio identical with that of the inside of the panel.
  • the stripe matrix type shadow mask having a high beam-permeability
  • the CRT for televisions or videos requiring high-brightness
  • the dot matrix type shadow mask having a fine-pitch
  • the CRT for computers or data processors requiring high-resolution
  • the public CRT requires high-brightness to display clear pictures on the screen which are capable of being viewed from a long distance.
  • the industrial CRT requires high-resolution to display distinct letters or symbols on the screen.
  • the CRT using a stripe matrix type shadow mask has a beam-permeability higher than that using a dot matrix type shadow mask.
  • the CRT using a dot matrix type shadow mask with a fine pitch has a resolution higher than that using the stripe matrix type shadow mask.
  • the permeability R of the electron beam is mathematically given by the following formula:
  • the permeability of the electron beam may be calculated by the permeability per unit area or the area of the beam-guide aperture per pitch area (horizontal pitch ⁇ vertical pitch).
  • the permeability R of the CRT using the dot matrix type shadow mask is about 17 to 19% while the permeability of the CRT using the stripe matrix type shadow mask is about 20 to 22%.
  • the permeability of a 15-inch industrial CRT using a dot matrix type shadow mask can be given by
  • the permeability R of a 17-inch industrial CRT using a dot matrix type shadow mask is given by
  • the permeability R of a 25-inch public CRT using a stripe matrix type shadow mask is given by
  • the CRT using a stripe matrix type shadow mask has a resolution unsuitable for industrial usage while the CRT using a dot matrix shadow mask has a brightness unsuitable for public usage. Therefore, one CRT cannot be used for both industrial and public purposes.
  • an embodiment of the present invention is directed to a CRT for multimedia which substantially obviates one or more of the problems due to the limitations and disadvantages of the related art.
  • An object of an embodiment of the present invention is to provide a method of making a multimedia CRT for simultaneously producing high brightness and high resolution.
  • the multimedia CRT includes a shadow mask having a plurality of beam-guide apertures.
  • Each of the beam-guide apertures has a stripe shape, and the ratio of the horizontal length of the effective screen to the horizontal pitch of the beam-guide apertures in the center of the shadow mask is in the range of 1:8.81 ⁇ 10 ⁇ 4 to 1:1.23 ⁇ 10 ⁇ 3 .
  • the ratio of the horizontal pitch of the beam-guide apertures in the center of the shadow mask to the thickness of the shadow mask is in the range of 1:0.25 to 1:0.56.
  • FIG. 1 is a partial sectional view of a multimedia CRT according to an embodiment of the present invention
  • FIG. 2 is a perspective view of a shadow mask according to an embodiment of the present invention.
  • FIG. 3 is a front view of a multimedia CRT showing the effective screen according to a preferred embodiment of the present invention
  • FIG. 4 is a sectional view taken along line A—A of FIG. 2;
  • FIG. 5 is a schematic diagram illustrating the relation of the shadow mask to the electron beam according to an embodiment of the present invention.
  • a multimedia CRT includes a shadow mask 10 having a plurality of stripe-shaped beam-guide apertures 22 where the ratio of the horizontal length L of the effective screen to the horizontal pitch P of the beam-guide apertures 22 in the center of the shadow mask 10 is in the range of 1:8.81 ⁇ 10 ⁇ 4 to 1:1.23 ⁇ 10 ⁇ 3 .
  • a multimedia CRT according to another preferred embodiment of the present invention includes a shadow mask 10 having a plurality of stripe-shaped beam-guide apertures 22 where the ratio of the horizontal pitch P of the beam-guide apertures 22 in the center of the shadow mask 10 to the thickness t of the shadow mask 10 is in the range of 1:0.25 to 1:0.56.
  • the multimedia CRT includes a front panel 4 having a phosphor screen 2 and a funnel 6 connected to the rear of the panel 4 .
  • the funnel 6 has a neck portion into which an electron gun 8 is fitted.
  • a shadow mask 10 is placed directly behind the phosphor screen 2 and supported by a mask frame 12 .
  • a plurality of stud pins 14 are fixed on the side interior of the panel 4 to support the mask frame 12 through corresponding hook springs 16 .
  • An inner shield 18 is further provided under the mask frame 12 to interrupt the influence of the earth's magnetic field.
  • an explosion proof band 20 is provided on the external sealing portion between the panel 4 and funnel 6 .
  • the shadow mask 10 has a masking portion 24 having hundreds of thousands of fine beam-guide apertures 22 , a closed peripheral portion 26 having no apertures, and a skirt portion 28 welded to the mask frame 12 .
  • Each of the beam-guide apertures 22 has a color selection function. That is, the red (R), green (G) and blue (B) beams are focused through the beam-guide aperture 22 to hit the selected phosphors on the phosphor screen 2 .
  • the pitch can be divided into a horizontal pitch P and a vertical pitch V.
  • the horizontal pitch P acts as the main pitch.
  • the present invention is directed to a multimedia CRT capable of simultaneously satisfying high-brightness and high-resolution requirements.
  • the beam-guide aperture 22 has a stripe shape capable of giving a relatively high beam-permeability R.
  • the stripe-shaped beam-guide apertures 22 (collectively referred to hereinafter as “stripes”) have a relatively small horizontal pitch P capable of ensuring an under-scanning condition.
  • the conventional 14 or 15-inch industrial CRT typically has a resolution of 640 ⁇ 480 or 800 ⁇ 600.
  • the 800 ⁇ 600 resolution CRT is preferably selected because it has the advantages of producing distinct images or large amounts of letters or symbols.
  • the inventive multimedia CRT is preferably a wide 24-inch CRT which has a 800 ⁇ 600 resolution and a 16:9 ratio of the width of the screen to the length of the screen.
  • FIG. 3 is a front view of a multimedia CRT showing a effective screen 4 a defined by a dotted line.
  • the area of the effective screen 4 a has a fixed value proportional to the CRT size.
  • an under-scanning condition where the image producing signals are scanned on the screen portion smaller than the effective screen 4 a by 0 ⁇ 10%, produces high resolution characteristics necessary for correct information display.
  • the diagonal length of the effective screen 4 a is 560 ⁇ 5 mm while the longitudinal length is 488 mm.
  • a resolution of 800 ⁇ 600 indicates the total number of stripes 22 formed on the shadow mask 10 . Therefore, the masking portion 24 of the shadow mask 10 has stripes 22 with 800 vertical lines and 600 horizontal lines.
  • the horizontal pitch P of the stripes 22 is given by:
  • the horizontal pitch P of the stripes 22 is 0.61 mm. This value practically becomes a maximum value relating to the horizontal pitch P of the stripes 22 .
  • Eq. 8 is applicable when a margin of 20% is allowed to the horizontal pitch P of the stripes while Eq. 9 is applicable when a margin of 30% is allowed.
  • the minimum value is 0.43 to 0.49 mm when computed in view of the maximum margin. Therefore, it is preferable that the horizontal pitch P of the stripes 22 is established at 0.43 mm or more.
  • Table 1 shows the results of calculating the resolution and brightness of the wide 24-inch CRT while varying the horizontal pitch P of the stripes 22 .
  • the resolution is determined by the focusing characteristic. That is, when the letters displayed on the periphery of the screen are unfocused, the resolution is bad.
  • the brightness is good when the brightness ratio of the periphery of the screen to the center of the screen is above 90% because the pitch ratio of the beam-guide holes in the center of the shadow mask to the beam-guide holes at the periphery of the shadow mask is the same.
  • the pitch ratio (110 to 140%) of the beam-guide holes at the center of the shadow mask to the beam-guide holes in the periphery of the shadow mask is different.
  • the brightness is good when the brightness ratio in the center of the screen to the periphery of the screen is above 50%.
  • the stripe pitch in the center of the shadow mask and the stripe pitch at periphery of the shadow mask differs with a medium range between the industrial CRT and the public CRT. Therefore, the brightness is good when the brightness ratio in the center of the screen to the periphery of the screen is above 75%.
  • Table 2 shows data measuring the brightness at the periphery of the screen when the brightness in the center of the screen is fixed with 35.5 ft-L.
  • the pitch P of the stripes is in the range of 0.43 to 0.60 mm when the brightness ratio in the center of the screen to the periphery of the screen is above 75% and, hence, is good.
  • the horizontal pitch P of the stripes is in the range of 0.43 to 0.60 mm and the optimum value of the horizontal pitch P is 0.55 mm.
  • the ratio H of the longitudinal length L of the effective screen 4 a to the horizontal pitch P of the stripes 22 in the center of the shadow mask 10 is established with 1:8.81 ⁇ 10 ⁇ 4 to 1:1.23 ⁇ 10 ⁇ 3 .
  • the multimedia CRT can have good brightness by making the beam-guide hole of the shadow mask into a stripe shape as well as high resolution by reducing the horizontal pitch of the stripe.
  • FIG. 4 is a cross sectional view taken along A—A line of FIG. 2 .
  • One-side or both-side etching is performed to the shadow mask 10 to thereby form a plurality of stripes 22 .
  • the shape of the stripe 22 is usually largely depressed in a one-sided direction.
  • W indicates the hole size of the stripe 22 passing the electron beam 34
  • TA indicates the horizontal length with respect to the left inclined side 30 of the stripe 22
  • TB indicates the horizontal length with respect to the right inclined side 32 of the stripe
  • B (called a “bar”) indicates the distance between the neighboring stripes 22 .
  • the size of the bar B is given by:
  • the inclined sides of the stripe 22 forms an inclination of 15 to 60° in accordance with the incidence angle of the electron beam 34 .
  • the stripes in the center of the shadow mask 10 may be vertically formed because the electron beam 34 is vertically incident upon the shadow mask 10 .
  • the inclined side of the stripe facing the center of the shadow mask 10 and having the horizontal length TA is formed with an inclination of 15° for easy processing.
  • the inclined side of the stripe facing the periphery of the shadow mask and having the horizontal length TB is formed with an inclination more than 15° in view of the deflection angle of the electron beam by a deflection yoke.
  • the horizontal lengths TA and TB (collectively indicated by “T”) with respect to the inclined sides 30 and 32 of the stripe 22 can be given by:
  • t is the thickness of the shadow mask 10 .
  • t is the thickness of the upper etching side.
  • t can be assumed to be the total thickness of the shadow mask 10 in view of the small error.
  • the horizontal lengths TA and TB with respect to the inclined sides 30 and 32 can be measured with the thickness of the shadow mask 10 and the incidence angle ⁇ of the electron beam 34 .
  • the maximum deflection angle ⁇ of the electron beam 34 is 46°, and the angle ⁇ is 11°, the incidence angle ⁇ of the electron beam 34 obtained from Eq. 13 is 35°.
  • the left inclined side 30 positioned toward the center of the shadow mask 10 is not particularly affected by the incidence angle ⁇ of the electron beam 34 .
  • it is formed with the conventional inclination of 15° enabling easy processing of the stripe 22 .
  • the horizontal length TA with respect to the left inclined side 30 is approximated by:
  • the width W of the stripes 22 is established with 0.160 mm.
  • the bar B of the stripes 22 is given by:
  • the bar B of the stripes 22 should be large enough to ensure the structural stability while reducing the horizontal pitch P of the stripes 22 .
  • the bar B of the stripes 22 can be computed by using Eqs. 12 and 15 as follows:
  • the bar B of the stripes 22 becomes larger, enabling micro-processing with respect to the stripes 22 .
  • the thickness t of the shadow mask 10 becomes thinner, the resulting structural weakness makes it difficult to form an appropriate curvature and may produce a doming phenomenon due to thermal expansion and a vibrating phenomenon due to the sonic pressure of the speaker.
  • the thickness t of the shadow mask 10 be more than 0.15 mm.
  • the thickness t of the shadow mask 10 is less than 0.15 mm, the stability and strength of the shadow mask 10 cannot be practically maintained.
  • the thickness t of the shadow mask 10 should be less than 0.24 mm.
  • the thickness t of the shadow mask 10 is more than 0.24 mm, the time required for the etching process increases and the smooth stripe formation suffers.
  • the thickness t of the shadow mask 10 is established between 0.15 and 0.24 mm, the range capable of keeping the appropriate bar B of the stripes 22 .
  • the ratio S of thickness t of the shadow mask 10 to the horizontal pitch P of the stripes 22 in the center of the shadow mask 10 is given by:
  • the ratio S of the horizontal pitch P of the stripes 22 in the center of the shadow mask 10 to the thickness t of the shadow mask 10 is approximated as:
  • the ratio S of the horizontal pitch P of the stripes 22 in the center of the shadow mask 10 to the thickness t of the shadow mask 10 is in the range of 1:0.25 to 1:0.56.
  • the inventive multimedia CRT it is possible to simultaneously realize high-resolution and high-brightness by establishing the thickness of the shadow mask and the horizontal pitch of the stripes with optimum values.
  • it can be used for public as well as for industrial purposes.
  • multimedia computer systems or televisions having an Internet connecting function to produce letters and pictures by incorporating various media.

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  • Electrodes For Cathode-Ray Tubes (AREA)
US09/691,416 1997-06-04 2000-10-17 Cathode ray tube for multimedia Expired - Fee Related US6342757B1 (en)

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US09/691,416 US6342757B1 (en) 1997-06-04 2000-10-17 Cathode ray tube for multimedia

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KR1019970023035A KR19990000255A (ko) 1997-06-04 1997-06-04 멀티미디어용 음극선관 및 그 제조방법
KR97-23035 1997-06-04
US6195298A 1998-04-17 1998-04-17
US09/691,416 US6342757B1 (en) 1997-06-04 2000-10-17 Cathode ray tube for multimedia

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030102794A1 (en) * 2001-11-10 2003-06-05 Lg. Philips Displays Korea Co., Ltd. Shadow mask for color CRT
US6922010B2 (en) * 2000-09-28 2005-07-26 Dai Nippon Printing Co., Ltd. Shadow mask for a cathode ray tube

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4859901A (en) * 1981-10-29 1989-08-22 U.S. Philips Corporation Color CRT shadow mask with wrinkle-free corners
US5928047A (en) * 1996-05-15 1999-07-27 Matsushita Electronics Corporation Planar member for shadow mask of cathode-ray tube and manufacturing method of shadow mask

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4859901A (en) * 1981-10-29 1989-08-22 U.S. Philips Corporation Color CRT shadow mask with wrinkle-free corners
US5928047A (en) * 1996-05-15 1999-07-27 Matsushita Electronics Corporation Planar member for shadow mask of cathode-ray tube and manufacturing method of shadow mask

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6922010B2 (en) * 2000-09-28 2005-07-26 Dai Nippon Printing Co., Ltd. Shadow mask for a cathode ray tube
US20030102794A1 (en) * 2001-11-10 2003-06-05 Lg. Philips Displays Korea Co., Ltd. Shadow mask for color CRT
US6664724B2 (en) * 2001-11-10 2003-12-16 Lg. Philips Display Korea Co., Ltd. Shadow mask for color CRT

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Publication number Publication date
KR19990000255A (ko) 1999-01-15
JPH117901A (ja) 1999-01-12

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